Conventionally, in a machine tool of this kind, as shown in FIG. 1, control instruction data from the tracing control apparatus 1 and the NC apparatus 2 are switched and transmitted selectively to the three-axis driving means for the tracer controlled machining 4 and the three-axis driving means for the numerically controlled machining 5 through switching circuits 3X, 3Y, and 3Z, in accordance with two selection signals S.sub.A and S.sub.B, wherein the selection signal S.sub.A and the selection signal S.sub.B are used as a tracer controlled machining selection signal and a numerically controlled machining selection signal, respectively.
When the tracer controlled machining selection signal S.sub.A is selected by the switching circuits, both the three-axis driving means for the tracer controlled machining 4 and the three-axis driving means for the numerically controlled machining 5 are occupied by the tracing control apparatus 1, as a result, both of these driving means are controlled by control instructions transmitted from the tracing control apparatus 1 through the switching circuits 3X, 3Y, and 3Z. Therefore, in this case, the movement of the tracer provided in the tracer-head at the tracer controlled machining side is transmitted to both the cutters which are provided at the tracer controlled machining side and at the numerically controlled machining side respectively. The predetermined tracer controlled machining is performed by one of those cutters or by both of those cutters simultaneously.
When the numerically controlled machining selection signal S.sub.B is selected by the switching circuits, both the three-axis driving means for the tracer controlled machining 4 and the three-axis driving means for the numerically controlled machining 5 are occupied by the numerical control apparatus 2. As a result both of these driving means are controlled by the control instructions from the numerical control apparatus 2 through the switching circuits 3X, 3Y, and 3Z. Therefore, in this case, the tracer provided in the tracer-head at the tracer controlled machining side is removed, and the control instruction from the numerical control apparatus is transmitted to both the cutters which are provided at the tracer controlled machining side and at the numerically controlled machining side respectively. The predetermined numerically controlled machining is performed by one of those cutters or by both of those cutters simultaneously.
In the switching circuit 3X shown in FIG. 1, 31 and 32 are AND gates receiving the control instruction from the tracing control apparatus 1 and the tracer controlled machining selection signal S.sub.A, 33 and 34 are AND gates receiving the control instruction from the numerical control apparatus 2 and the numerically controlled machining selection signal S.sub.B, 35 is an OR gate receiving the output signal from the AND gate 31 or 33 and supplying the predetermined instruction to the three-axis driving means for the tracer controlled machining 4, and 36 is an OR gate receiving the output signal from the AND gate 32 or 34 and supplying the predetermined instruction to the three-axis driving means for the numerically controlled machining 5. The switching circuits 3Y and 3Z are constituted similarly.
In the three-axis driving means for the tracer controlled machining 4, 41, 42, and 43 are motors which drive the X axis, Y axis, and Z axis, respectively, in accordance with the control instruction supplied to the driving means 4. Reference numerals 44, 45, and 46 are position detectors, each of which detects the movement of the tool or the table in each axial direction. Position data detected by the position detectors 44, 45, and 46 are fed back through a feedback circuit F.sub.1 to the tracing control apparatus 1 and the numerical control apparatus 2. Thereby, each of the control apparatuses monitors the position data of the tool or the table driven by the driving motors.
In the three-axis driving means for the numerically controlled machining 5, 51, 52, and 53 are motors, which drive the X axis, Y axis, and Z axis, respectively, in accordance with the control instruction supplied to the driving means 5. Reference numerals 54, 55 and 56 are position detectors, each of which detects the movement of the tool or the table in each axial direction. Position data detected by the position detector 54, 55, and 56 are fed back through a feedback circuit F.sub.2 to the tracing control apparatus 1 and the numerical control apparatus 2. Thereby, each of the control apparatuses monitors the position data of the tool or the table driven by the driving motors.
Three pairs of the switching circuits 3X, 3Y, and 3Z are used in order to switch the circuit. The X-axis driving motors 41 and 51, which are provided in the driving means 4 and 5, respectively, are controlled by the control instruction transmitted through the switching circuit 3X. Similarly, the Y-axis driving motors 42 and 52, which are provided in the driving means 4 and 5, respectively, are controlled by the control instruction transmitted through the switching circuit 3Y. Further, the Z-axis driving motors 43 and 53, which are provided in the driving means 4 and 5, respectively, are controlled by the control instruction transmitted through the switching circuit 3Z.
In this apparatus of the prior art, when the numerically controlled machining selection signal S.sub.B is selected, the three-axis driving means for the tracer controlled machining is also occupied by the numerical control apparatus. Therefore, there is a problem that the three-axis driving means for the tracer controlled machining is idling when it is not necessary to perform the numerically controlled machining with both the cutters which are provided at the tracer controlled machining side and at the numerically controlled machining side, simultaneously.
Also, when the tracer controlled machining selection signal S.sub.A is selected, the three-axis driving means for the numerically controlled machining is also occupied by the tracing control apparatus. Therefore, there is a problem that the three-axis driving means for the numerically controlled machining is idling when it is not necessary to perform the tracer controlled machining with both the cutters which are provided at the tracer controlled machining side and at the numerically controlled machining side, simultaneously.